New Duck nest found

As I went out to get the paper this morning, I disturbed a mother duck that had laid one egg. I did not see her until she flew away.
She sat in my front yard for awhile but has now gone. The egg is uncovered. I am afraid I scared the mother away and she will not return. Should I cover the egg a bit?

This is a question I would ask a local wildlife rehabber. Covering it won't keep it warm enough, I think. So if you want to keep it viable, I think you'd need to keep it closer to 95F. I am not a hatcher, though.